Most pregnant teenagers are not eating an adequate diet, putting their babies' health at risk, research finds.

A report, published by the Maternity Alliance and the Food Commission, says that in many cases this is because they cannot afford to eat healthily.

The research, based on interviews with 46 pregnant teenagers, found most ate a diet high in fat but low in healthy fruit and vegetables.

Nutritional analysis of the diets showed deficiencies in several essential vitamins and minerals, such as vitamin A, magnesium, folic acid, zinc, iron and calcium.

I normally fill myself up on bread or crisps or chocolate because it's cheap

Pregnant 16-year-old

The report showed two thirds of pregnant teenagers living away from family had a food budget of less than £20.25 per week - the estimated cost of a 'modest but adequate' diet.

The same number said that their diet worsened as money ran out, as they started to eat less food and fill up on cheap, unhealthy food such as chips.

Christine Gowridge, director of Maternity Alliance, said: "Pregnant teenagers receive significantly less benefits than mothers over the age of 25.

"Yet their dietary needs, and the needs of their growing babies, are the same, if not more.

"How can we expect teenage mothers to be able to eat healthily on less than £3 per day for food?"

Diet on the day before being interviewed

Almost two-thirds had consumed no fruit or fruit juice

Two-fifths had consumed no vegetables or salad

One in five had consumed neither fruit nor vegetables

Only two out of the 46 women surveyed were eating the recommended five portions of fruit and vegetables per day

Women on a poor diet during pregnancy are more likely to have low birthweight babies.

That increases their baby's risk of poor health during childhood and during their adult life.

Tim Lobstein, director of the Food Commission, said: "Without sufficient cash, no amount of nutrition information, and no amount of cooking skills, will help these women protect the health of their babies."

The teenagers who took part in the survey were generally aware of what a healthy diet should consist of, and many were making efforts to improve their diets.

All said they had received dietary advice during their pregnancy.

But most said they simply could not afford to follow it.

Benefit reform

The report's authors are calling for welfare benefits to be available as soon as women confirm their pregnancy - rather than having to wait until they are 29 weeks pregnant when the baby's need for nutrients has already peaked.

They also want all pregnant women to be entitled to at least the same benefits as the current rates for women aged over 25.

At present, benefits for 16-17 year olds are complex and depend on the young woman's circumstances.

For a pregnant 16 or 17-year-old in full-time education living at home, her parents can claim £38.50.

If she is eligible to claim benefit in her own right she can get £32.90 a week, or in some circumstances, including where she can show she is estranged from her parents, £43.25.

Some young women of 16 and 17 may not be eligible for any benefit, even if they are pregnant and living independently.

The benefit rate for a woman aged 18-24 is £43.25, and for a woman aged 25 or over, £54.65.